Process for upgrading natural sas condensates



March 9, 1965 N. J. PATERSON PROCESS FOR UPGRADING NATU'A SAS CONDENSATES Filed July 27, 1962 NOLLVI'IILSICI INVENTOR NORMAN J. PA TE RSON 3,172,84l PRCESS FR UFGRAENG NATURAL GAS CCNDENSATES Norman li. Paterson, San Rafaei, Calif., assigner to California Research Corporation, San Francisco, Calif., a corporation of Delaware Filed .iuly 27, 1962, Ser. No. 212,823 Ciaims. (ill. 298-79) This invention relates to the conversion of hydrocarbons. More particularly, it is concerned with the production of high octane motor fuels of adequate volatility from full-boiling condensates by an improved process comprising a series of interdependent and interrelated steps whereby increased utilization of the combined hydrogen in the feed stock is obtained.

Recent gas condensate discoveries and the current construction of large pipelines to transport natural gas have increased the importance of the problem of economic disposal of heavier by-product liquid hydrocarbons that are produced in conjunction with natural gas. Wlth increasing emands for gasolines of higher antiknock ratings for use as motor fuels, the problem of disposing of increased quantities of natural gas condensates has become critical.

The usual methods for upgrading straight run naphthas, such as hydrogenative reforming over noble metal catalyst, have not been found satisfactory for the needed upgrading of natural gasoline liquids. Numerous other processing schemes have been studied with the view of improving the position of the natural gasoline producer in the motor fuel market. The prior art discloses processes involving isomerization of the C5 and C6 fractions of the knatural gasoline employing either noble metal or aluminum chloride-type catalyst. These processes have not been successful in achieving desired high octane levels and volatilities at acceptable yields since the octane levels obtained at equilibrium isomerizat-ion fall short of the values required to permit blending of these products in present high octane motor fuels. In addition, separation of the desired isomers of desired high octane quality is difficult to achieve and is uneconomic. It has further been proposed to upgrade the C5 and C6 fractions by low pressure-high temperature dehydrogenation over chromium cataiyst-on-alumina support. The products from this type of process, while improved in octane, are highly olenic and resulting gasoline blends are unsatisfactory with respect to road performance and stability. In addition, a considerable increase in equipment size is required due to the low pressure operation.

Thus, present-day rening processes for upgrading fullboiling condensates, including integrated operations, do not obtain optimum realization ofthe combined hydrogen present in the feed stock. This is reflected in the product distribution and quality which falls short of the theoretical obtainable. Therefore, it would be desirable if a method were available for processing full-boiling condensates and converting at least some of the higher boiling portions thereof (boiling above about 375 F.) into high octane motor fuels of adequate volatility in a manner that more fully utilizes the hydrogen content of the charged stock.

It is an object of this invention to produce more valuable products from full-boiling condensates.

lt is another object of this invention to convert fullboiling condensates to more valuable products by a process that eiciently utilizes the combined hydrogen of the condensate.

Another object of this invention is to produce high yields of high octane gasoline comprising primarily isoparaflins and aromatics.

Still another object is to provide a process for the production of substantially saturated high octane gasoline of adequate volatility possessing enhanced lead susceptibility to mixtures of lead alkyls including physical mixtures and redistributed mixtures of the lead isomers.

A further object -is to produce high yields of gasoline and fuel components by converting a portion of the feed heavier than gasoline by hydrocracking with the production of minimum quantities of heavier oils and fuel gas.

The invention will be more clearly understood, and further objects and advantages thereof will be apparent, from the following description when read in connection with the accompanying drawing. The drawing is a diagrammatic illustration of an embodiment of process units and flow paths suitable for carrying out the process of the present invention.

In a broad aspect, the process of the present invention comprises distilling a full-boiling condensate 20 to 60 volume percent of which boils above 375 F. to produce naphtha and at least one gas oil fraction, reforming in a reforming zone at least a portion of said naphtha to produce hydrogen, hydrocracking in a hydrocracking zone at least a portion of said gas oil in the presence of at least a portion of said hydrogen, reforming at least a portion of the resulting hydrocracked gasoline to produce additional hydrogen, passing at least a portion of said additional hydrogen to said hydrocracking zone, and recovering from the :system nished gasoline having a high octane number and loW olefin content.

In a more specific embodiment, the process of the present invention comprises distilling a full-boiling condensate 20 to 60 volume percent of which boils above 375 F. under substantially atmospheric pressure to separate gasoline, at least one higher boiling fraction and a bottoms product, subjecting a heavier portion of `said gasoline to reforming in the presence of hydrogen and a platinum-alumina-halogen catalyst at a temperature from about 750 to about l0O0 F. and a pressure of from about 50 p.s.i. to about 1000 p.s.i. to thereby produce a net yield of hydrogen, hydrocracking at least a portion of said higher boiling fraction in the presence of hydrogen from the reforming step to produce gasoline and passing at least a portion of the gasoline thus produced to said reforming .step to produce additional hydrogen.

The composition and properties of condensates will i vary widely depending primarily on the physical state of the field-producing reservoir. Broadly speaking, condensates can be classiiied into two general groups: gasoline condensates and full-boiling condensates. Thus, gasolinetype condensates will have about zero to 20 volume percent of material boiling above 375 F. compared to Whole condensate which will have 20 to 60 volume percent boiling above 375 F., as measured by a true boiling point distillation of moderate efficiency. A typical ASTM distillation and other properties of a gasoline condensate from Woods County, Texas, and a full-boiling range condensate from Cass County, Texas, are shown below:

Gasoline Couden- Full-Boiling Consate Woods County, densate Cass Texas County, Texas Fraction Fraction Yield, LV, percent 100 10 100 42 Gravity, API 59 35 55 36 Aniline Point, F 114 118 143 172 Sulfur, wt. percent.-. 0.09 0. 20 0. 5 0.8 Nitrogen, ppm. Tota l0 30 16 ASTM Distillation, D-86 D-158 D-S D-1160 tart 89 377 88 375 10% 134 390 165 425 30%..- 189 420 250 455 234 480 335 540 90% 409 585 730 Eud Point 580 700 58() 950 Percent Recovery 97. 5 97 5 85 99 Referring now to the drawing, debutanized whole condensate is passed through line 1 into distillation column 2 where it is separated into various fractions. A light straight run naphtha With an end boiling point of about 180 F. is removed overhead from column Z through line 3 and is passed into depentanizer 4. From depentanizer 4 a bottoms fraction, essentially comprising hexanes, is passed through line 5 to storage, and an overhead pentane cut is passed through line 6 to deisopentanizer 7. From deisopentanizer 7 isopentane is Withdrawn overhead through line 8 and normal pentane is Withdrawn through line 9 to storage.

From distillation column 2 a heavy straight run naphtha having a boiling range of about 180 to 375 F. is passed through line to reforming zone 16. From distillation column 2 a fuel oil fraction boiling from about 375 to 520 F. is Withdrawn through line 17, and another fuel oil fraction having a boiling range of about 520 to 750 F. is withdrawn through line 18. A small amount of bottoms or reduced crude is Withdrawn from the bottom of distillation column 2 through line 19 and is passed to storage.

At least a portion of the fuel oil in line 17 is passed through lines and 21 to heater 22. At least a portion of the fuel oil in line 18 is passed through lines 23 and 2.1 to heater 22. The fuel oil mixture in line 21 is contacted with a stream of recycle hydrogen, prepared as herein- :after described, owing into 4line 21 through line 24, and also is contacted with a recycle stream from the hydrocracking unit hereinafter described flowing into line 21 through line 2S. The combined stream entering heater 22 through line 21 is heated to the desired temperature in heater 22 and the heated mixture is passed through line 35 into hydrocracking zone 36.

Hydroeracking zone 36 may be a conventional hydrocracking unit containing a conventional hydrocracking catalyst, for example nickel sulfide on silica-alumina, and may operate at conventional hydrocracking conditions. These conditions include a pressure of at least 500 p.s.i.g., preferably 800 to 3000 p.s.i.g., a temperature of about 400 to 850 F., a hydrogen feed rate of about 1500 to 30,000, preferably about 3000 to 15,000 s.c.f. per barrel of total feed, and a liquid hourly space velocity of about 0.2 to 15, preferably about 0.4 to 3.0.

From hydrocracking zone 36, light ends are passed through line 37 to a gas plant (not shown), a C5 to 180 F. light hydrocracked gasoline is Withdrawn as a product through line 38, and a 180 to 375 F. heavy gasoline is passed through line 39 to reforming Zone 16.

The gasoline that is produced in hydrocracking zone 36 predominates in soparains and naphthenes. It is particularly desirable as a charge for reforming processes wherein dehydrogenation of the naphthenes is one of the predominant reactions. Accordingly, the final reformed gasoline will contain isoparafns and aromatics.

From hydrocracking zone 36 material boiling higher than gasoline is recycled through line 25. If desired, a portion of this material may be withdrawn through line 40 and, because it is substantially saturated and free from aromatics, it may be used as a high quality diesel or jet fuel stock.

From reforming zone 16 hydrogen produced therein is passed through line 24 to hydrocraeking zone 36, and hydrogen is recycled through line 41 to reforming zone 16. From reforming zone 16 light ends are Withdrawn through line 4Z and a high octane C4-5-reformate gasoline is withdrawn through line 43.

The feeds to the hydrocraclring zone in the process of the present invention, prepared from Whole condensates, generally are low in nitrogen content (less than 100 ppm.) and do not require hydroiining prior to processing in the hydrocracking step. This results in economies in plant construction. Any minor nonhydrocarbon impurities in the feed stock, such as nitrogen and sulfur, are

converted in the hydrocracking and reforming steps to ammonia and hydrogen sulfide.

The following examples further illustrate various features and advantages of the process of the present invention, and compare said process with conventional processmg.

Example 1 A Cass County, Texas, full-boiling debutanized condensate of 55 API is charged at the rate of 10,000 barrels per day to an atmospheric distillation column. 1735 barrels per day of to 180 F. end point naphtha are removed overhead. A heavy naphtha side cut of 3865 barrels per day having a boiling range of to 375 F. is withdrawn as the first side cut. In addition, there are Withdrawn as additional side cuts 2100 barrels per day of 375 to 550 F. boiling range kerosene and 2100 barrels per day of 550 to 750 F. boiling range gas oil. A small amount of heavier material, reduced crude, is withdrawn as a bottoms product from the distillation column at a rate of 200 barrels per day.

The kerosene and gas oil side cuts, totalling 4200 barrels per day, are combined with hydrogen in such a proportion that the molal ratio of hydrogen to hydrocarbon is about 6:1. The combined stream is heated to a temperature of about 650 F. The heated mixture is passed over a bed of hydrocracking catalyst comprising nickel sulfide on silica-alumina and containing about 6 Weight percent nickel. The mixture may be passed either upiioW or downflow through the catalyst bed. rlChe space velocity in the hydrocracking step is 0.8 and the total hydrogen partial pressure is 1300 p.s.i.a. The gasoline product, C5 to 375 F. boiling range, produced in the hydrocracking step amounts to 3980 barrels per day; and all material boiling above 375 F. is recycled to extinction. In addition to the gasoline, there is also produced 890 barrels per day of butanes consisting of 630 barrels per day isobutane and 260 barrels per day normal butane. It will be noted that the liquid volume percent yield based on the charge to the hydrocracking step is 116 volume percent. This increase in volume is due to the decrease in density that is eifected in the molecular weight of the charge stock and to the small production of methane, ethane, propane and catalytic carbon.

The gasoline produced in the hydrocracking step is distilled to remove 1260 barrels per day of a C5 to 180 F. boiling range light gasoline which is characterized by a high isoparain content, and 2720 barrels per day of a heavy naphtha (180 to 375 F. boiling range) cornposed principally of isoparains and naphthenes. The material heavier than 375 F. is recycled to the hydrocracking zone to extinction. The heavy naphtha boiling from 180 to 375 F. is combined with hydrogen and the 180 to 375 F. boiling range straight run naphtha and the mixture is reformed in the presence of a conventional noble metal on alumina reforming catalyst. The operating conditions include an average catalyst temperature of 915 F., a liquid hourly space velocity of 2.0 and a pressure of 500 p.s.i.g. An 82 volume percent yield, i.e., 5400 barrels per day, of reformed gasoline having an octane number of 100.5 F-l-i-B ml. TEL per gallon is produced in the reforming step. There is a net production of hydrogen from the 6585 barrels per day of reformer charge stock of 880 s.c.f. per barrel of hydrocarbon feed. Since the 4200 barrels per day of feed to the hydrocracking step consumes about 1300 s.c.f. per barrel of hydrogen, the process is selfsuicient in hydrogen.

The total gasoline pool blended to 10 pounds Reid vapor pressure with butane is 8720 barrels per day of 97.0 F-1+3 ml. TEL per gallon octane number. Thus,

einem YLe the total products produced from 10,000 barrels per day of full-boiling condensate feed in this example are:

Barrels per day Gas, EFO 1 400 Excess isobutane 630 Excess normal butane 260 10 pound RVP gasoline 97.0 F-l-i-S ml.

TEL/gallon 8,720 Heavy fuel oil 200 Total 10,210

1EF'O (equivalent fuel oil) is amount of 10 API bunker fuel that would have equivalent heating value in Btu., assuming that one barrel of said fuel oil has a heating value of 0.3M Btu.

Example 2 By comparison, processing the same amount of condensate by conventional processing including atmospheric distillation and catalytic reforming of the heavy straight run naphtha to 100.5 F-1i3 ml. TEL per gallon octane number would give 4985 barrels per day of l pound RVP gasoline of 94.4 F-l-i-33 m1. TEL per gallon octane number. The total products obtained by conventional processing would be:

Barrels per day Gasoline, EFO 1 600 pound RVP gasoline 94.4 F-l-l-3 ml.

TEL/gallon 4,985 Gas oils 4,200 Heavy fuel oil 200 Total 9,985

1 Equivalent fuel oil.

The following example demonstrates the advantages of the process of the present invention for producing from full-boiling condensates high yields of high octane gasolines having balanced and adequate volatilities and excellent road octane numbers.

Example 3 Case I.A conventional renery processing 10,000 barrels per day of full-boiling condensate, reforming the 180 to 375 F. heavy naphtha at a severity of 100.5 F-1|-3 ml. TEL per gallon. Premium gasoline is produced by blending isopentane distilled from the condensate along with high octane reformate. Regular gasoline is a blend of reformate and light straight run naphtha.

Case [1 -Same as Case I, but with recycle isomerization of normal pentane and once-through isomerization of normal hexane produced from the condensate. Premium gasoline is a blend of isopentane and high octane reformate, and regular gasoline is a blend of hexanes and high octane reformate.

Case IIL- An integrated processing scheine as defined by the present invention whereby heavy gasoline is reformed to 100.5 F-l-l-3 ml. TEL per gallon to produce net hydrogen which is used to hydrocrack the material heavier than gasoline, separating a light gasoline from the hydrocracking step and reforming the heavy gasoline from the hydrocracking step to supply additional hydrogen. Premium gasoline is produced by blending of light hydrocracked gasoline with high octane reformate, and regular gasoline is produced by blending light straight run (45 to 50%) with high octane reformate. Both grades are improved in octane number by the addition of redistributed mixtures of lead alkyls.

Case I Case II Case III Refinery Input, b.ld. 10,000 Debu- Whole b./d. tanized Condensate Production, b./d.:

Pool Gasoline 4, 985 4, 920 8,720 F-l-l-3 ml. TEL/gal 94. 4 97. 5 97, 2 ASTM 50% Temperature, 195 19S 205 Premium Gasoline 840 2,000 4, 440 Percent of Total Po 16. 9 40. 7 50. 9 F-1+2.5 Inl. TEL/gal. 100 100 99. 5 FJH-2.5 ml. Alkyl 1 Equivalent of TEL Road Octane at 2.5 ml. Lead (Calculated) 99. 8 99. 8 99. 8 ASTM 50% Temperature, F 235 235 204 Regular Gasoline 4,145 2,920 4, 280 Percent of Total Pool- 83.1 69. 3 49. l Ml. TEL to 93.0 F-l 3.0 1.9 2. 7 Ml. of .alkyl Equivalent TEL 1 to 93.0 F-l 1. 9 ASTM 50% Temperature, F.. 182 172 206 1 MLA with 50% Et Allryls, 50% Me Allryls:

TEL.. 3. 65

EtgMe. 13.98

EtzMe2 20.01

EtMeg. 12. 71

TML 3. 02

Total Alkyls 53. 37

From the foregoing examples, it may be seen that, compared with conventional processing, the process of the present invention produces high yields of gasoline of excellent antiknoclr value and excellent storage stability due to absence of olefins. It desired, the hydrocracking step can be operated once-through or with partial recycle of material heavier than gasoline to produce a high cetane diesel fuel and 'a low freeze point, high smoke point jet fuel. Hydrogen balance is maintained under these condir tions by increasing the end point of the heavy gasoline produced on the atmospheric distillation tower and the hydrocraclrer in order to provide additional reforming feed stock. Thus, the process of the invention achieves outstanding results in product distribution and quality from full-boiling condensates by (l) the favorable hydrogen `distribution obtained by a combination of hydrocracking and reforming whereby the heavier portions of the condensate are converted into high quality gasoline while low octane naphtha is upgraded with the concomitant production of hydrogen and (2) the hydrocracking step operates with the catalyst that minimizes gas formation Since the formation of large amounts of methane, ethane and propane would result in a large loss of hydrogen from the process.

In addition to the high yields. of gasoline and self-sufficiency in hydrogen realized by the process, gasolines of adequate and balanced volatility and high octane number are produced. Present-day demands call for gasolincs having research octane numbers in the range of 90 to 100. While it is commercially feasible to obtain fractions of the required octane number at the higher end point of the gasoline range, it is more diflicult to prepare light gasoline fractions of high octane number to blend with the heavier high yoctane material. Since present-day gasolines are required to have both high octane and high volatiltiy, there is a demand for a processing yroute which will impro-ve octane number without adversely aifecting Volatility. Generally, it is desired to have both premium and regular gasolines of desired volatilities so that the ASTM 50% point is between 190 and 240 F. In addition to the above features, increased emphasis is currently directed to producing gasolines of high road octane number. This requires, in addition to high research octane numbers, gasolines having low sensitivities such las can be obtained from mixtures of aromatics and isoparaflins.

ln summary, the process of the present invention:

(l) Produces from condensates high yields of motor fuels having adequate and balanced volatilities and composed of mixtures of isoparafns and aromatics and characterized by high research and road octane numbers, ex-

'7 cellent storage stability and freedom from sulfur and oletins.

(2) Provides an integrated process for upgrading condensates that is self-suliicient in hydrogen.

(3) Provides processing flexibility which permits high quality diesel and jet fuels to be produced from condensates in addition to high octane gasoline; by control of the distillation cut points on the atmospheric and hydrocracking distillation columns, the aforesaid different products may be produced in varying proportions as desired.

What is claimed is:

1. A process which comprises distilling a full-boiling range condensate under substantially atmospheric pressure to separate a light straight run gasoline fraction of 80 to 180 F. boiling range, a heavier gasoline fraction having a boiling range of 180 to 375 F., at least one heavier fraction boiling between 375 and 750 F., and a bottoms product, subjecting at least a portion of said heavier gasoline to catalytic reforming under conditions that result in a net production of hydrogen, hydrocracking at least a portion of said heavier fraction boiling between 375 and 750 F. in the presence of hydrogen from the reforming step to produce a hydrocraclced gasoline product rich in isoparai'iins and boiling from 80 to 375 F., separating said hydrocraclced product into light 80 to 180 F. gasoline and heavy 180 to 375 F. gasoline, passing a suiiici'ent portion of said heavy 180 to 375 F. hydrocracked gasoline to said reforming step to produce suicient additional hydrogen to maintain the system in hydrogen balance, blending said light hydrocracked gasoline with reformate to produce a premium gasoline and blending said light straight run gasoline with reformate to give a regular gasoline, both gasolines having good and balanced volatility.

2. A process in accordance with claim 1 further characterized in that the catalytic reforming catalyst is a platinum-alumina-halogen type and the reforming step is operated at a temperature of 750 to 1000 F. and a pressure of 50 to 1000 p.s.i.g. and severity suiiicient to give a debutanized reformate of at least 95 clear research octane in order to provide sufficient hydrogen for the hydrocracking zone.

3. A process in accordance with claim l further characterized in that said hydrocracking catalyst comprises nickel sulde on silica-alumina, said catalyst containing 0.5 to 20 weight percent nickel.

4. A process in accordance with claim l further characterized in that said premium gasoline blend contains 25 to 40 volume percent light gasoline from said hydrocracking zone and said regular gasoline contains to 55 volume percent of light straight run gasoline, in each case together with sufcient high octane reformate to produce gasolines with ASTM temperatures between 190 and 240 F.

5. The process of claim 1 further characterized in that at least 2.0 ml. per gallon of alkyl equivalent TEL is added to said premium gasoline.

6. A process for upgrading natural condensates which comprises distilling a full-boiling condensate 20 to 60 volume percent of which boils above 375 F. to produce naphtha and at least one gas oil fraction, reforming in a reforming zone at least a portion of said naphtha to produce reformed naphtha and hydrogen, hydrocracking in a hydrocracking zone at least a portion of said gas oil in the presence of at least a portion of said hydrogen to produce a gasoline rich in isoparaiins, reforming a sutlicient portion of said hydrocracked gasoline to produce sufficient additional hydrogen to maintain the system in hydrogen balance, passing at least a portion of said additional hydrogen to said hydrocracking zone, and recovering from said reforming zone and from said hydrocracking zone finished gasoline having a high octane number and low olefin content.

References Cited by the Examiner UNITED STATES PATENTS 2,3 60,622 10/ 44 Roetheli 208-80 2,956,002. 10/ 60 Folkins 208--110 2,987,466 6/ 61 Senger et al. 208-110 3,008,895 1/61 Hansford et al 208-112 3,016,344 6/ 62 Kirsch 208-79 ALPHONSO D. SULLIVAN, Primary Examiner. 

1. A PROCESS WHICH COMPRISES DISTILLING A FULL-BOILING RANGE CONDENSATE UNDER SUBSTANTIALLY ATMOSPEHERIC PRESSURE TO SEPARATE A LIGHT STRAIGHT RUN GASOLINE FRACTION OF 80* TO 180*F. BOILING RANGE, A HEAVIER GASOLINE FRACTION HAVING A BOILING RANGE OF 180* TO 375*F., AT LEAST ONE HEAVIER FRACTION BOILING BETWEEN 375* AND 750*F., AND A BOTTOMS PRODUCT, SUBJECTING AT LEAST A PORTION OF SAID HEAVIER GASOLINE TO CATALYTIC REFORMING UNDER CONDITIONS THAT RESULT IN A NET PRODUCTION OF HYDROGEN, HYDROCRACKING AT LEAST A PORTION OF SAID HEAVIER FRACTION BOILING BETWEEN 375* AND 750*F. IN THE PRESENCE OF HYDROGEN FROM THE REFORMING STEP TO PRODUCE A HYDROCRACKED GASOLINE PRODUCT RICH IN ISOPARAFFINS AND BOILING FROM 80* TO 375*F., SEPARATING SAID HYDROCRACKED PRODUCT INTO LIGHT 80* TO 180*F. GASOLINE AND HEAVY 180* TO 375*F. GASOLINE, PASSING A SUFFICIENT PORTION OF SAID HEAVY 180* TO 375*F. HYDROCRACKED GASOLINE TO SAID REFORMING STEP TO PRODUCE SUFFICIENT ADDITIONAL HYDROGEN TO MAINTAIN THE SYSTEM IN HYDROGEN BALANCE, BLENDING SAID LIGHT HYDROCRACKED GASOLINE WITH REFOMATE TO PRODUCE A PREMIUM GASOLINE AND BLENDING SAID LIGHT STRAIGHT RUN GASOLINE WITH REFORMATE TO GIVE A REGULAR GASOLINE, BOTH GASOLINES HAVING GOOD AND BALANCED VOLATILITY. 